Schiff-Base System of Glutaraldehyde Crosslinked Chitosan-Algae-Montmorillonite Clay K10 Biocomposite: Adsorption Mechanism and Optimized Removal for Methyl Violet 2B Dye

Abstract

Heren, chitosan (CH), algae (AL), and montmorillonite clay K10 (MK10) were used in the hydrothermal synthesis of a new Schiff-base system of glutaraldehyde-crosslinked chitosan-based biocomposite (CH-AL-MK10/GL) for the removal of a model cationic dye [MV (2B)] from aqueous environments. Various analytical methods were employed to evaluate the characteristics of the synthesized biocomposite (e.g., BET surface analysis method, elemental analysis, FTIR, SEM–EDX, XRD, and point of zero charge). The key adsorption parameters (CH-AL-MK10/GL dose, pH, and time) were optimized using the BBD model and the optimum adsorption (%) value of 86.4% was achieved at the following operating conditions: CH-AL-MK10/GL dose: 0.99 g/100 mL, pH: 8.3, time: 418 min and a quadratic model was generated for predicting the dye removal values based on the adsorption conditions. The adsorption equilibrium data revealed great compatibility with the pseudo-second order kinetic model and Langmuir and Freundlich isotherm models, achieving a maximum adsorption capacity of 98.3 mg/g at 25 °C. Hence, the adsorption of MV (2B) by CH-AL-MK10/GL was through chemisorption in an initially monolayered fashion which then proceeds to a multilayered model after the surface layer reaches a saturated state. The results of all the characterization methods as well as the adsorption equilibrium studies were utilized to determine the possible interactions between the CH-AL-MK10/GL surface and MV (2B) dye molecules and the electrostatic forces, hydrogen bonding, Yoshida hydrogen bonding and n- π stacking interactions were concluded to be responsible for the adsorption process.